The present invention relates to an optical recording medium capable of recording and reproducing voice and images. More particularly, this invention relates to an optical recording medium having a layer for printing (xe2x80x9cprint layerxe2x80x9d) formed thereon.
Only a few years ago, the CDs (Compact Disc) dedicated for reproducing once stored audio data or for installing once stored computer software were very popular. These CDs had a considerably large storage capacity as compared to the FDs (Floppy Disc), but they required a costly and big scale hardware for recoding data. In recent years, optical recording media called CD-Rs (CD-Recordable) and a CD-RWs (CD-Rewritable) in which data can be recorded at ease have appeared in market and have become very popular. These CD-Rs and CD-RWs use CD-format and make it possible for a common man not only to reproduce the sound or data stored therein, but also record the sound or data using a small scale and low cost recording device.
When analog information such as audio (for example, songs) or visual (for example, photos) information are recorded as digital information, then identical tone or image quality can be obtained if the information is recorded with an identical format. Moreover, theoretically, it has been proved that no degradation of data occurs even if the digital information is copied for what ever number of times. However, it is has been recognized based on sensory evaluation that tone or image quality changes, although slightly, depending on the material used to manufacture the optical recording mediums and the conditions under which the manufacturing is carrier out.
The reasons why such differences occur include signal errors, noise arising due to flow of an excessive currents in a servo system for signal read pickup, electrification and/or magnetization of the surfaces of optical recording mediums and the like. However, the exact cause is not yet known.
The above-stated problems can be roughly solved by following three technical approaches. That is,
(1) by preventing the irregular reflection of a signal read light beam in an optical recording medium;
(2) by suppressing the vibration of the optical recording medium; andc
(3) by preventing or eliminating the electrification and magnetization of the surface of the optical recording medium.
The irregular reflection of a signal read light beam in an optical recording medium listed as (1) above may be prevented with the following methods. That is, as disclosed in, for example, Japanese Utility Model Unexamined Application Publication No.5-5483, a material that absorbs the irregularly reflecting light may be applied on the surface or sides of the optical recording medium. Moreover, as disclosed in, for example, Japanese Patent Application Laid-open No. 5-334601, a sheet or an adapter having a hue that absorbs the irregularly reflecting light may be applied on the surface or sides of the optical recording medium. Moreover, as disclosed in, for example, Japanese Patent Application Laid-open No. 11-328727, the irregularly reflecting light may be discharged from the sides of the optical recording medium.
The vibration of an optical recording medium listed as (2) above may be suppressed with the following methods. That is, as disclosed in, for example, Japanese Patent Application Laid-open No. 6-60589, a sheet may be stick on the surface of the optical recording medium. On the other hand, a heavy weight may be mounted on the optical recording medium during reproduction. The function of the heavy weight may be provided to the sheet that may be provided for suppressing the irregularly reflecting light from the optical recording medium. This method, however, involves the following risks. Because of the thickness of the sheet, the overall thickness of the optical recording medium increases and it cannot be mounted on the apparatus that reads/writes from/in the optical recording medium. Moreover, if the sheet is not attached to a position at which it should be attached, then the optical recording medium becomes eccentric thereby degrading the tone quality. If the sheet is pilled-off because of any reason, then the reflection layer of the optical recording medium gets damaged.
The magnetization and electrification or static electricity of the surface of the optical recording medium listed as (3) above may be suppressed or prevented with the following methods. That is, as disclosed in, for example, Japanese Patent No. 2942760, a demagnetizer may be used. Moreover, as disclosed in, for example, Japanese Patent Unexamined Application Publication No. 11-246833, pattern-cuts may be provided to the optical recording medium.
Nevertheless, these conventional techniques cannot provide sufficiently satisfactory results and demand for an optical recording medium capable of conducting higher-grade recording and reproduction for audio and visual information is, therefore, rising.
Thus, the conventional techniques have both merits and demerits and do not furnish a satisfactory solution. That is, they do not satisfy requirements of providing thin, light, inexpensive optical recording mediums without mass eccentricity and available to various reproduction apparatuses. The method of suppressing vibration by sticking a sheet on the optical recording medium, in particular, involves the following risks as already stated above. Because of the thickness of the sheet, the optical recording medium cannot be set in the reproduction apparatus. Moreover, if position of the sheet shifts, then the mass eccentricity of the optical recording medium increase thereby degrading the tone quality. Moreover, if the sheet is removed from the optical recording medium, the reflection layer of the medium get damaged.
It is an object of the present invention to provide an optical recording medium capable of ensuring high-grade recording and reproduction if applied to, in particular, the recording and reproduction of sound information (audio information) and image information (visual information).
It is another object of the present invention to provide an optical recording medium capable of ensuring high-grade recording and reproduction while suppressing the influence of an external dynamic factor (e.g., vibration) by adjusting the constitution of a print layer.
The present invention is intended to provide an optical recording medium which can improve tone quality by suppressing the vibration of the medium, which is markedly thin, lightweight and available to any types of reproduction apparatuses, which is excellent in surface smoothness and appearance, which can suppress mass eccentricity, that is, to provide an optical recording medium capable of realizing high-grade recording and reproduction if applied to the recording and reproduction of audio and visual information and the like.
The optical recording medium according to one aspect of the present invention comprises at least a transparent substrate, a reflection layer, and a print layer. The print layer is characterized in that it has a multilayer structure in which a plurality of ink layers made from different inks that have different specific gravities are stacked.
The optical recording medium according to another aspect of the present invention at least comprises a transparent substrate; a reflection layer; and a print layer. The print layer has a multilayer structure in which a plurality of ink layers made from different inks that have different specific gravities are stacked. If recording and/or reproducing is conducted using a recording and reproduction apparatus having a function of scanning a recording and reproduction light spot on the optical recording medium by rotating the optical recording medium, then a frequency component xcex1m of a vibration amplitude at the number of vibration n times as large as the number of vibration corresponding to the number of rotation of the optical recording medium among vibration amplitudes on an outermost periphery of the optical recording medium has a characteristic to satisfy a relationship of xcex1mxe2x89xa6xcex1sxc3x970.5 with a frequency component xcex1s of a vibration amplitude at the number of vibration n, where n is an integer equal to or greater than 1, times as large as the number of vibration corresponding to the number of rotation of the substrate of the optical recording medium among vibration amplitudes on an outermost periphery of the substrate, the substrate solely put on a same rotation system as a rotation system for the optical recording medium.
The optical recording medium according to still another aspect of the present invention at least comprises a transparent substrate; a reflection layer; and a print layer. The print layer has a multilayer structure in which a plurality of ink layers made from different inks that have different specific gravities are stacked. If recording and/or reproduction is conducted using a recording and reproduction apparatus having a function of scanning a recording and reproduction light spot on the optical recording medium by rotating the optical recording medium, then a frequency component xcex1m(f) of a vibration amplitude on an outermost periphery of the optical recording medium has a characteristic to satisfy a relationship of ∫xcex1mdfxe2x89xa6∫xcex1sdfxc3x970.4, where 1 Hzxe2x89xa6fxe2x89xa6100 Hz, with a frequency component xcex1s(f) of a vibration amplitude on an outermost periphery of a substrate of the optical recording layer, the substrate solely put in a same rotation system as a rotation system for the optical recording medium.
The method of manufacturing the optical recording medium according to still another aspect of the present invention is a method of manufacturing the optical recording medium comprising at least a transparent substrate, a reflection layer, and a print layer. This method comprises the step of forming the print layer from a plurality of ink layers formed from different inks that have different specific gravities, wherein at least one of the ink layers is formed by overprinting the same ink a plurality of times.
The optical recording medium according to still another aspect of the present invention comprises a recording layer for optically recording a signal; a reflection layer for reflecting recording and reproduction light; and a transparent substrate on which the recording layer and the reflection layer are provided. The transparent substrate is provided with a recording and reproduction guide groove which is scanned with a laser light to optically read the signal according to a change of an intensity of the reflected laser light. Moreover, a print layer comprising a plurality of ink layers stacked one above another is formed on one surface of the reflection layer. Each ink layer has inorganic substances dispersed in a resin. Moreover, the print layer has a region, having a thickness of 0.5 xcexcm or more and 5 xcexcm or less, in a layered fashion on an entire surface of the print layer such that the region contains no inorganic particles having diameter 0.5 xcexcm or more.